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766

Appendix T.

i\

And these quantities may be ascertained for other points of the
stroke by measuring similar intercepts along horizontal lines.

It will be noticed that the steam always tends to become
drier toward the end of the stroke (due to re-evaporation), though
never becoming entirely so ; and the value of compounding in
drying the stearn is also apparent. (See Appendix //.,/ 878.)

P. 608. Adiabatic of Saturated Steam.Zeuner gives
the following empirical formula to find the value of the exponent
n in the equation to the adiabatic for saturated steam :

#= i'035-f ("i x dryness fraction).

from which it would appear that Rankine's curve is suitable for
steam having 25 percent, of suspended moisture, while Zeuner's
curve is for stearn initially dry.

P. 6op. Expansion of Wet Saturated Stearn.It has
been already pointed out that the saturation curve is a curve of
lowering temperature. Also that the compression of dry satu-
rated stearn at constant temperature causes it to become wet by
partial condensation, because steam at a given temperature can
only exist at a certain pressure. Conversely, the expansion of
stearn at constant temperature will tend to dry it; but if there be
sufficient water present, the pressure will not fall during the ex-
pansion, and therefore the curve on the diagram would be a
horizontal straight line.

Calculation of Specific Volume of Dry Saturated
Steam, when the temperature, pressure, and latent heat are
known.

. 756.

Dealing with i Ib. weight of steam, whose volume and pressure
are shewn at A, Fig. 756 :